Epidemiological studies have demonstrated an increased risk of developing B-cell lymphomas in patients with chronic hepatitis C virus (HCV) infection. However, the strength of the association shows great geographic discrepancies, with higher relative risk in countries with high HCV prevalence. It remains unclear whether additional environmental and genetic factors are involved or if the international variability is simply a consequence of the variable infection prevalence. Therefore, a causal relationship remains controversial. Other confounding factors may affect the comparability of the different studies, including the method of HCV assessment, the selection of normal controls, the lymphoma classification used, and the year of publication. The most convincing proof is the observation, mainly limited to some indolent subtypes, of B-cell lymphoma regressions after HCV eradication with IFN and ribavirin. However, the molecular mechanisms of the HCV-induced lymphomagenesis are mainly hypothetical. According to the model considered to be most plausible, lymphoma growth is a consequence of the continuous antigenic stimulation of the B-cell immunologic response induced by the chronic viral infection. This review summarizes the current epidemiological and biological evidence of a role of HCV in lymphomagenesis, describing the putative mechanisms for a causative relationship. The clinical characteristics and management difficulties of the HCV-associated lymphomas are also discussed. HCV treatment with IFN cannot be given safely in concomitance with cytotoxic lymphoma treatment because of hematological and liver toxicity. However, novel and better tolerated antiviral regimens are under development and will hopefully make the treatment of both lymphoma and hepatitis easier in the future.